Insect antifeedant activity associated with compounds isolated from species ofLonchocarpus andTephrosia

The antifeedant activity of a series of 21 chalcones, flavanes, and flavanones isolated from the generaLonchocarpus andTephrosia (Leguminosae) was assessed by behavioral and electrophysiological bioassays against larvae ofSpodoptera littoralis andS. exempta. The antifeedant activity is related to the molecular structure of the compounds, and possible modes of interaction with the insect taste receptors are discussed.     

Allelochemics and nutritional indices for larch sawfly,Pristiphora erichsonii (Hartig): A specialist feeding onLarix spp.

Nutritional indices for larch sawfly,Pristiphora erichsonii (Hartig), larvae fed single and tufted needles of fourLarix spp. are reported. Larvae offered only single needles ofL. lancina, L. russica, andL. decidua had lower relative growth rates than larvae fed tufted needles of the same species. There was no significant reduction in larval growth for larvae fedL. kaempferi single needles as compared to tufted needles. Abietic acid-treated foliage reduced consumption but did not lower relative growth rate. These findings are discussed with respect to the mechanism of preferential feeding of the larch sawfly and current hypotheses of host plant herbivore interaction.Research supported by the School of Natural Resources, College of Agricultural and Life Sciences, University of Wisconsin—Madison under a grant from the McIntire-Stennis Program, Project 2243.     

Patterns of Bioactivity and Herbivory on Nothofagus Species from Chile and New Zealand

Nothofagus species from Chile and New Zealand were surveyed in the field for invertebrate abundance and leaf feeding damage and in the laboratory for antifeedant activity against leafrollers (Ctenopsteustis obliquana, Epiphyas postvittana), deterrent activity against pea aphid (Acyrthosiphon pisum), insect growth regulatory activity (Oncopeltus fasciatus), nematicidal activity (Caenorhabditis elegans), antibiotic activity (Pseudomonas solanaciarium), and general toxicity. A data matrix indicated that N. alessandri and N. pumilio most likely have a chemical barrier to insect attack as leaves showed low faunal abundance, low herbivory, and activity in the leafroller antifeedant, aphid deterrent, and nematicidal assays. A chemical examination of N. alessandri that used the leafroller antifeedant test to guide the separation yielded an active fraction containing the flavonoid, galangin, and the stilbene, pinosylvin, which appear to act in concert to deter leafroller feeding. The discovery of the phytoalexin, pinosylvin, in the leaves, raises the possibility that Nothofagus in general, and N. alessandri in particular, may have induced chemical defense mechanisms.     

青蒿素及其衍生物对菜青虫的生物活性

以二氢青蒿素为原料合成了10种双二氧青蒿素醚和5种单二氢青蒿素醚,用常规的非选择性叶碟法测定了质量浓度为1.0 g/L的合成化合物、青蒿素和二氢青蒿素对菜青虫的生物活性.结果表明:双醚对菜青虫的拒食活性最为显著,处理后24、48 h的拒食率分别为85.4%～96.9%和90.9%～98.6%,单醚分别为45.5%～60.6%和50.9%～68.2%,二氢青蒿素为36.6%和42.4%,青蒿素为40.1%和47.0%;双醚同样具有较高的杀虫活性,其处理后96 h的校正死亡率为72.7%～95.5%,单醚为45.4%～54.6%,二氢青蒿素为49.9%,青蒿素的杀虫活性不显著.结合活性数据,初步讨论了青蒿素衍生物的构效关系.     

拟康定乌头中二萜生物碱成分及拒食活性

[目的]为了研究拟康定乌头中化学成分及其拒食活性.[方法]利用正反相硅胶柱层析进行分离纯化,结合HR-ESIMS、IR、1D和2D NMR等波谱技术对分离得到的化合物结构进行鉴定,采用叶碟法测试了其中10个化合物对甜菜夜蛾3龄幼虫的拒食活性.[结果]共分离得到15个二萜生物碱.其中10个化合物均存在一定的拒食活性.[结...     

不同大蒜精油成分及生物活性对比分析

为了解白皮大蒜和紫皮大蒜精油成分及生物活性差异,采用水蒸气蒸馏法提取白皮大蒜和紫皮大蒜精油,通过气相色谱质谱联用仪(GC-MS)分析测定两种大蒜精油的可挥发性成分;用对倍稀释法研究两种大蒜精油对几种常见病原菌的抑制活性;采用小叶碟法测定两种大蒜精油对斜纹夜蛾的拒食活性;并检测白皮、紫皮大蒜精油对ABTS、DPPH和OH自由基的清除作用。结果表明:白皮大蒜精油鉴定出26种成分,占精油的95.79%;紫皮大蒜精油鉴定出22种成分,占精油的94.26%,主要杀菌物质大蒜辣素和大蒜新素在紫皮大蒜(59.34%)中的含量比白皮大蒜(50.11%)多;两种大蒜精油对实验用菌有明显抑制作用,尤其紫皮大蒜精油对枯草芽孢杆菌、白色念珠菌、热带假丝酵母菌和板栗疫病的抑制效果比白皮大蒜好;白皮大蒜和紫皮大蒜精油对斜纹夜蛾24h平均拒食率分别为52.97%和100%;白皮大蒜精油对ABTS和DPPH自由基的清除率高于紫皮大蒜精油,对OH自由基的清除率基本相当。     

Antifeedant and toxic effects of sesquiterpenes fromSenecio palmensis to colorado potato beetle

A bioassay-guided fractionation of the aerial parts ofSenecio palmensis resulted in the isolation of two sesquiterpenes, 2,10-bisaboladien-1-one and 11-acetoxy-5-angeloyloxy-silphinen-3-one. The bisabolene and the silphinene represented 0.012% and 0.024% of the plant dry weight, respectively. Both compounds showed antifeedant activity againstLeptinotarsa decemlineata larvae and adults in short-term choice and no-choice bioassays. Both compounds were also tested against different species of phytopathogenic fungi. The beetles were more sensitive to these compounds in choice than in no-choice assays, with a gradient of increasing sensitivity from second instars to adults. Bisabolene was 45 times less active as an antifeedant than juglone, which was tested as a positive control. The silphinen was more active than the bisabolene, with a range of activity similar to juglone. Furthermore, exposure of fourth instars to these compounds over a 24-hr period resulted in reduced feeding and growth rates. To distinguish between antifeedant and toxic effects, growth efficiencies were calculated as the slope of the regression of relative growth rate on relative consumption rate. The comparison of these results with those of antifeedant simulation and contact toxicity bioassays indicates that feeding inhibition is the primary mode of action of the bisabolene, while the silphinene shows both antifeedant and toxic effects.     

Identification of cantharidin in false blister beetles (Coleoptera,Oedemeridae) from florida

Cantharidin, a potent vesicant and antifeedant, is identified for the first time in two oedemerid beetles from the western hemisphere. Amounts of the substance per beetle were found to range from 2 to 7 g inHeliocis repanda and from 15 to 35 g inOxycopis thoracica. Females had two to three times more cantharidin than males of the same species. Cantharidin loads of these beetles are sufficient to irritate human skin.     

Action of Extracts of Apiaceae on Feeding Behavior and Neurophysiology of the Field Slug Deroceras reticulatum

A systematic examination was made of the plant family Apiaceae (Umbelliferae) in which extracts of 33 species, representing 32 genera, were screened for antifeedant activity against the field slug Deroceras reticulatum by using an electrophysiological recording assay. In this assay, the olfactory sensory epithelium of the posterior tentacle of the slug was exposed to volatile components of the plant extracts presented in an airstream, and any subsequent activity of the olfactory nerve was recorded. Extracts of 22 species elicited a range of nervous activity in the preparation. A feeding bioassay was used to measure any change in consumption when extracts were added to a standard food. Statistical analysis of data obtained from both electrophysiological traces and the feeding bioassays identified extracts of Petroselinum crispum, Conium maculatum, and Coriandrum sativum as being the most neuroactive as well as the most antifeedant.     

The influence of dietaryβ-carboline alkaloids on growth rate,food consumption,and food utilization of larvae ofSpodoptera exigua (Hubner)

-Carboline alkaloids are found worldwide in many plant families. Harman, harmine, and other simple -carboline alkaloids were tested for activity against a generalist phytophagous insect, the beet army worm [Spodoptera exigua (Hubner)]. Chronic dietary exposure tests (neonate to pupa) reveal potent antifeedant and possible toxic effects. Acute dietary exposure tests on fifth-instar larvae also demonstrate antifeedant activity.